In the co-assigned U.S. Pat. No. 4,114,785 (1978) a pneumatic outlet is disclosed including a lading valve comprising a circular segment body portion and a moment portion extending outwardly from the body portion. The lading valve is movable between open and closed positions by an operating shaft having a pair of handles which are respectively located at either end of the outlet. The weight of the lading applies a moment to the body portion of the valve and thus tends to rotate the lading valve toward open position.
To prevent the lading from moving the lading valve to open position in transit, a preset torque is applied to the operating shaft by a Belleville spring held in engagement with a shoulder on the shaft by a threaded plug in a direction opposite to the diameter of rotation of the valve to open position. In this arrangement the threaded plug and Belleville spring apply a longitudinal force to the operating shaft which is reacted at the opposite end wall of the outlet. In this way the valve may be fixed in a desired partially open or metering position. The load on the operating shaft is transferred to the lading valve. In practice the amount of preload torque applied by the plug has varied due to varying tolerance limits between the valve and the end wall. In some instances the lading valve has been bent and in some instances the lading valve has been difficult or impossible to open.